The present invention relates to a zoom lens of a compact size composed of seven elements in seven groups divided into a front group having a negative refracting power and a rear group having a positive refracting power.
There have heretofore been known zoom lenses comprising seven elements in seven groups divided into a front group having a negative refracting power and a rear group having a positive. refracting power as disclosed in Japanese Patent Publication No. 55-13334 and Japanese earlier Publication No. 56-43619, for example The known zoom lenses are designated with an iris diaphragm mechanism incorporated in a space between lenses in the rear group.
With such diaphragm design, the lens groups positioned forward and rearward of the iris diaphragm mechanism have to be coupled together across the iris diaphragm mechanism sandwiched therebetween, and hence the lens barrel is complex in construction. This is disadvantageous in point of lens assembly.
If an aperture is positioned in front of the rear group, then the rear group can be unitized as a whole. Such an arrangement aids in point of lens barrel construction, lens assembly, and cost. However, since a space is needed between the front and rear groups for accommodating the iris diaphragm mechanism therein, the lens cannot be rendered compact in size.